Miter clamp



Jan. 9, 1940. w KRUMBACH 2,186,198-

MITER CLAMP Filed Aug. 19, 1937 I N wax/7'02 W/'// A rombac/m 14 T'TOENEY Lil , ed portions I 2, being 'spaced'by an intermediate Patented Jan. 9, 1940 UNITED STATES PATENTLQOFFICE "MITERCLAMIP Will Krumbach, Highland Park, Ill, assignor to Adjustable Clamp Company, Chicago, 111,, a corporation of Illinois Application August/19, issmserial o. 159,918

3Claims. (c1.144 29s)' uniquely constructed for convenient detachable visible faces or edges of the finished work, which readily enables accurate fitting and adjustment ofthe joint-parts during the clamping operation,

and which is rugged, durable, and exceedingly economical in construction and efficient in use and operation.

And with the above and other objects in view, my invention resides in the novel features of form, construction, arrangement, and combination of parts presently described and pointed out in the claims.

In the accompanying drawing, 7

Figure l is a plan view of a clamp of miter type constructed in accordance with and embodying my present invention; a

Figure 2 is a vertical longitudinal sectional view of the clamp, taken approximately along the 1 line 2-2, Figure l; and

Figures 3, i, and 5 are enlarged fragmental elevational views ofslightly modified forms of work-gripping members forming part of the clamp of my invention.

Referring nowinmore detail and by reference characters to the drawing, which illustrates a preferred embodiment of the present invention, the clamp comprises a hand-screw in the form preferably ofa suitably elongated cylindrical bar A equipped for a portion of its, length with a. right-hand thread I and for another portion of its length with a left-hand thread 2, such threadnon-threaded or plain portion 3, and suitably fixed on an end'of bar A for convenience in manipulation of the clamp, is a suitable co-axial hand-grip 4.

1 B, B, designates blocks, which are respectively provided with oppositely threaded bores, as at 5,-for accommodating engagement with, and for relative threaded adjustment by, the correspondingly'oppositely threaded bar-portions I, 2, the

blocks B, B, being also formed with axially aligned transverse plain or smooth bores, as at rightangles to their faces 01 to a depth preferably in parallel relation to, the bores 5, as best seen in Figure 2.

Fixedin, and extending lengthwise through, the plain bores ii, are respective tubular sleeves '5 each preferably havmg length to extend equia distantly outwardly on opposite side's'of'its respective supporting-block, and each having an internal diametrical dimension for snuglyslidably accommodating for free longitudinal movement a co-axially disposed cylindrical guide-rod C for l1? retaining the blocks B, B, in upstanding parallel relation, the rod C being preferably upset or otherwise enlarged at its extremities, as at 8,for limiting its longitudinal movement and preventing its'ccmplete withdrawal-from the sleeves 1,

Preferably integrally formed with, and extending outwardlyindiametrically opposed relationship to the bores 5, 6, from the lower or base end b, of the blocks B,B, are respective worker:- gaging members or grippers 9, each preferably diametrically reduced or counter-bored for a portion of its length intermediateits ends, as at c, all for purposes presently more fully appearing and as best seen in Figure 2.

In use and operation, two work or wooden 231 members D, D, are sawed or otherwise formed and shaped for miterjoint formation in any conventional manner, the particular members D, D,

respective upper faces at with recesses or sockets 35 10, which are preferably disposed symmetrically and equidistantly on opposite sides of the une 'ture line of the joint, and which extend downwardly into the respective members D, D, at

somewhat in excess of one-half the thickness of thewood.

The screw-bar A is then axially turned in one direction, whereupon the blocks B, B, are shifted away from each other a sufficient distance so as to'permit the grippers 9 to be seated in the respective recesses or sockets 1B. The screw-bar r A is then axially turned in the opposite direction, I whereupon the work-gripping blocks B, B, are drawntoward eachother until the work-members D, D, are brought into loose abutting engagement along the juncture line 7', when the members D, D, may be slidably moved or shifted with respect to each other for precise and exact joint forming abutment; suchshifting movement being freely permitted through the pivoted engagement of the grippers 9 with the members D, D.

Thus, during the initial adjustment, the member D is out of proper joint-forming alignment with the member D and in the position shown in dotted lines in Figure l and the clamp will be disposed in the position also shown in dotted lines in Figure 1. However, through, as stated, the unique engagement of the blocks B, B, with the members D, D, the members D, D, may be relatively shifted with respect to each other and thereby brought into precise alignment, as shown in full lines in Figure 1, in which position the I clamp will extend transversely across and normal to the juncture line 7', also as shown in full lines in Figure 1. When the members D, D, have been so precisely aligned, the screw-bar A may be tightened down to first complete the clamping of the joint and then to rigidly retain the members D, D, in butt-wise engagement during the setting and hardening of any interposed adhesive.

Since, in the case of a joint formation between fairly thick members, there is some slight tendency for the. joint to buckle, that is to say, to open up slightly along the finished face under clamping pressure, it has been found desirable to cut away or relieve the grippers 9, as shown at 0, so that the clamp-pressure Will be applied substantially at the center of the material of the work-members D, D, any buckling tendency of such members being thereby entirely overcome.

For certain types of work, it has been found desirable or preferable to provide a block 13 having a work-engaging or gripping member 9 of frustro-conical contour, as shown in Figure 3.

For other types of work, it may be preferable to provide a block 15 having a work-engaging or gripping member 9" of integral pin-like contour, which may be driven into the work. This particular type of work-gripping member is especially adapted for employment in the formation of miter joints in thin, lightweight struc: tures, such as picture frames, or under other circumstances where the particular work-members to be joined do not permit the formation of recesses orsoekets similar to the recesses l0; and it may be here stated that the blocks of the particular clamp may be provided with removable work-grippers, so that a wide variety of differently shaped work-grippers may be utilized according to the specific requirements of the particular joint being formed.

The clamp may also be of so-called universal type as particularly shown in Figure 5. In this form of the clamp, the blocks. B while equipped with work-grippers 9, are somewhat thickened or freely accommodating suitably sized nail-like grippers 9", the blocks B in practice, being inverted, so that their normal fiat top faces I) may be placed flatwise upon the particular workmembers and the nails or grippers 9 driven downwardly thereinto. And it may be stated in this connection that it has been found preferable to arrange the bores -e, so that their respective axes lie in a single plane, and it has been stated that, by permitting the grippers 9" to be driven diagonally into the work-members, the joint-forming force exerted by the clamp will be imposed upon the nail-like grippers 9 substantially as shear stress, thereby practically eliminating any bending forces which might otherwise distort the grippers 9 and impair the strength of the joint.

Further, if desired, I may also provide a bridgelike member H, which may be pinned or otherwise fixed or secured at its one extremity to the center portion of the guide-rod C and provided at its outer extremity with a transversely extending bore 12 for rotatably accommodating the smooth intermediate portion 3 of the handscrew A, all as best seen in Figure 5, the bridgemember ll functioning not only in maintaining the guide-rod C in permanently centered relationship with respect to the screw-bar A, but

, also in eliminating any bowing or binding of the guide-rod C withrespect tothe screw-bar A which may otherwise result when the clamp is .used on large joints requiring excessive amounts of clamping pressure.

Thus, by my present invention, I provide a unique form of clamp, which is convenient in use and operation, is economical in construction, and which is so formed as to enable simple and efficient clampwise installation upon the work and precise and accurate adjustment of the workmembers in joint-forming relation.

It should be understood that other changes and modifications in the form, construction, arrangement, and combination of the several parts of the clamp may be made and substituted for those herein shown and described without departing from the nature and principle of my invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A clamp comprising, in combination, a pair of companion blocks each having a pair of parallel transverse bores, one of said bores being smooth, the other of said bores being threaded, and the threads of the latter bores being oppositely disposed, means including a rod lengthwise extending loosely through the set of smooth bores of the blocks for retaining the blocks shiftably in operative alignment, means on the block directly engageable in the work pieces being clamp-ed for detachably securing the blocks to said work, and a bar having oppositely threaded portions engaging the threaded bores of the blocks for drawing the blocks together for securing the work-members in buttwise-joint-forming engagement.

2. A clamp comprising, in combination, a pair of companion blocks each having a pair of parallel transverse bores, one of said bores being smooth, the other of said bores being threaded, and the threads of the latter bores being oppositely disposed, means including a rod lengthwise extending loosely through the set of smooth bores of the blocks for retaining the blocks shiftably in operative alignment, means includ- I ing projections on the blocks diametrically reduced intermediate their ends for insertion into the work-members for securing the blocks pivotally to the work-members and for bringing the clamping pressure to bear upon the work-members interiorly of their outer faces, and a bar having oppositely threaded portions engaging the threaded bores of the blocks for drawing the blocks together for securing the work-members in buttwise-joint-forming engagement.

3. A clamp comprising, in combination, a pair of companion blocks each having a pair of parallel transverse bores, one of said bores being smooth, the other of said bores being threaded, and the threads of the latter bores being oppositely disposed, means including a rod lengthwise bers, and a bar having oppositely threaded por- I extending loosely through the set of smooth bores of the blocks for retaining the blocks shiftably in operative alignment, means including projections on the blocks of frustro-conical contour for insertion into the work-members for detachably securing the blocks pivotally to the work-memtiens engaging the threaded bores of the blocks for drawing the blocks together for securing the work-members in buttwise-joint-forming. engagement; t t t v I WILL KRUMBACH. 

